Temp Control Refrigeration
Hello All: Control guru’s posted this one in the refrigeration thread, little response. Any control tech like at it..
Found faulty Ranco temperature controller for salad bar unit. Second time finding controller set point out of range, was at 188 deg set point not allowing unit to run. The first call about 1 month ago I locked out touch pad to rule out operator era. Upon arrival today was out of range again. I replaced with new ranco controller and unit operates normally again, reaching set point.
Cycling unit a few times with 2 minute equalization times I noted compressor starting a little jerky once, but had to leave for another emergency call, I plan to return to check starting components & compressor. Believe unit is a (PSC) compressor with run capacitor, but did not get an exact match on Tecumseh IOM web site.
Thinking of isolating the new ranco via ‘isolation cube relay’ so the ranco closes the isolation coil only and not the current relay to start components, just incase I might be getting some back 'EMF' from compressor to ranco causing the ranco to malfunction. (My question is do I need an additional 110v circuit for the contact side of relay to truly isolate ranco? As there is only 1 circuit under salad bar. Has any one had any issues with ranco's flaking due to back emf?) Any chime in on a proper isolation procedure is appreciated.
P.S. There is a adjacent salad bar unit under same salad bar that they don’t use. Believe separate circuit and same amperage, will confirm. I could run some flex from this unit over for isolation contact side to unit in question, for better isolation.
Following is model of Tecumseh compressor
Model: AKA9463ZXAXC (2 FLA)
Ranco: Single stage (L38-382) Contact rated 16A FLA
That's an odd one, its been a few years and I have not used the Ranco digital stuff for temp control.....
Used a ton of Johnson's digital stuff, I believe the419A?? never had an issue...
Back EMF is an interesting theory though, are you using something like a SPP6 or something for start up? A properly sized Mar's relay and start cap??
I would like to know what you find out though, I have a boat load of "C" stores that I take of.......
just curious, is this a kairak unit?
something is going on with our ranco controls located in the kairak units, the restaurant will have a power outage and within the next six months we will change all the temp controls in the restaurant. This is not one restaurant, any of my restaurants with kairak units have this proble, the controls will just lose the memory function! They are not controling the unit directly either, they are either going through a control relay or controling a solenoid valve!